#include <iostream>
#include <vector>
#include <algorithm>
#include<queue>
#include <string>
#include<stack>
#include<map>
using namespace std;

class Solution {
public:
    int singleNumber(vector<int>& nums) {
        int ans = nums[0];
        map<int,int> hashmap;
        for(int i=0;i<nums.size();i++){
            hashmap[nums[i]] += 1;
        }
        return ans;
    }
};

int main()
{
    vector<int> nums = {4,1,2,1,2};
    Solution solution;
    int ans = solution.singleNumber(nums);
    cout<<ans<<endl;
    return 0;
}